Abstract: A fabricating method for a one-piece refractory metal rocket engine chamber is described. Hollow liner sections of a platinum group metal or alloy are inserted into a chamber barrel portion to form the combustion chamber, connecting into a conical portion, a venturi throat and into a second conical portion, forming an expansion nozzle exit of the chamber. The hollow liner sections correspond to the interior shapes of the chamber portions. A refractory metal split hollow mandrel completes an assembly which is subjected to a hot isostatic pressing cycle. This HIP cycle expands the hollow mandrel, supporting the liner, outward against the chamber wall, pressure bonding the liner sections to the chamber portions. Scarfed edges of the liner sections are also bonded. The split mandrel is then chemically removed from the chamber resulting in a lined rocket engine chamber.